This invention relates to a surgical and diagnostic device wherein an operative element is alternately ejected from and drawn back into the distal end of a tubular introducer member. Such a device is particularly useful in minimally invasive surgery. The operative element may take the form of a specimen retrieval net, a cauterization snare, or other diagnostic or therapeutic structure.
Endoscopic retrieval devices include a tubular introducer sheath, an elongate shifter wire extending through the sheath and carrying a pouch at a distal end. When outside of the introducer sheath, the pouch is held open by a loop. Upon capture of a specimen, the loop and pouch are withdrawn partially into the tubular member to close the pouch and trap the specimen. Sometimes, it is necessary or desirable to extend and open the pouch again. However, if the loop has been retracted in its entirely into the sheath, the nose of the loop can catch on the pouch when the loop is ejected from the tubular member. The loop then buckles and the efficacy of the pouch is compromised. This catching of the loop nose on the pouch and the buckling of the loop happen particularly when the device includes a tether that causes the net to bunch up when the retrieval loop and pouch are being withdrawn into the tubular sheath. Cauterization snares with such tethers are disclosed in U.S. Pat. No. 5,759,187.